In the UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving the data rates, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing high-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (see, for example, non-patent literature 1).
In the third-generation system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. In the LTE system, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band that ranges from 1.4 MHz to 20 MHz. In the UMTS network, a successor system of the LTE system (referred to as, for example, “LTE-Advanced” or “LTE enhancement” (hereinafter referred to as “LTE-A”)) is under study, for the purposes of further broadbandization and higher speed.
In downlink of the LTE system (for example, Rel. 8), the CRS (Cell-specific Reference Signal) is defined. This CRS is used to demodulate user data, and, besides, used to measure downlink channel quality (CQI: Channel Quality Indicator) for scheduling and adaptive control, and so on. In the successor system of LTE (for example, Rel. 10), on the downlink, the CSI-RS (Channel State Information-Reference Signal) is defined as a reference signal for determining CSI (Channel State Information), including CQIs, PMIs (Precoding Matrix Indicators) and RIs (Rank Indicators).